[PATCH] Enable multiple file selection in File Browser dialog

Currently one can choose only one file from the file browser dialog, and in some circumstances multiple selection would be useful.

This patch enables multiple selection of files and images (but not directories), and makes this feature available for Python addons via xbmcgui.Dialog.browse() on a backward compatible manner.

The patch is filed under http://trac.xbmc.org/ticket/10894.

Example usage: I want to manage my photo collection and Picasa albums via my XBMC HTPC. For this reason I've got a Picasa plugin, which can upload photos to my webalbums, however until now I had to upload them one-by-one, which is quite painful.